Dimension reduction is the major consideration for designing an optical imaging lens in recent years. When reducing the length of the optical imaging lens, however, achieving good optical characteristics becomes a challenging problem.
U.S. Patent Publication No. 2011/0299178 disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements. The refracting power of the first lens element is negative, but that of the second lens element is positive. The third lens element is concave on the whole image-side surface thereof and the fourth lens element is convex on the whole image-side surface thereof. With these designed shapes and refracting powers, the lengths of some imaging lens reach 18˜19 mm. Such configuration fails to achieve preferable small size of the whole system as well as good optical characteristics.
U.S. Patent Publication No. 2011/0242683, 2011/0188132, and 2011/0188133 all disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements. The refracting powers of the first two lens elements are negative. However, the great air gap existing between the first two lens elements is unfavorable for shortening the length of the optical imaging lens.
U.S. Pat. Nos. 7,345,830, 7,375,903, 8,253,843 and U.S. Patent Publication No. 2010/0157453 all disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements. Although the refracting powers of the first and second lens elements are preferable positive and negative in order, the air gap between the first and the second lens elements is great for the concave image-side surface of the first lens element and the concave object-side surface of the second lens element. Therefore, the length of the optical imaging lens is not shortened.
Additionally, U.S. Pat. Nos. 7,365,920, 7,274,515, 7,920,340, 7,777,972, 8,179,470, 7,957,079, 8,218,253, 8,228,622 and U.S. Patent Publication No. 2012/0013998 and 2012/0266670 all disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements. However, the configurations of the lens elements thereof are unfavorable for improving the optical aberrations and meanwhile shortening the length of the optical imaging lens.
Therefore, there is needed to develop optical imaging lens with a shorter length, while also having good optical characters.